The mean annual incomes of certified welders are normally distributed with the mean of $50,000 and a standard deviation of $2,000. The ship building association wishes to find out whether their welders earn more or less than $50,000 annually. The alternate hypothesis is that the mean is not $50,000. If the level of significance is 0.10, what is the critical value?
A) +1.645
B) -1.282
C) ±1.282
D) ±1.645

Question

Quizplus · Accepted Answer

Since the alternate hypothesis is two-tailed (the mean is not equal to $50,000), the critical value will be found using a z-score table and a level of significance of 0.10 (or 0.05 on each tail). Consulting a z-score table, the critical values for a two-tailed test with a significance level of 0.10 are ±1.645. Therefore, the answer is D.

The Mean Annual Incomes of Certified Welders Are Normally Distributed